Effects of wearing a surgical mask on thermoregulation and respiratory parameters during exercise with hyperthermia-induced hyperventilation

The increase in core temperature during exercise in a hot environment causes hyperventilation (hyperthermia-induced hyperventilation), which decreases the partial pressure of arterial blood carbon dioxide. However, the effects on the body of wearing a surgical mask during exercise that would cause hyperthermia-induced hyperventilation have not been clarified. Therefore, we investigated such effects. Ten healthy men participated in the study. A 44-minute steady-state load cycling exercise (55% of peak oxygen uptake) was performed under hot environmental conditions (30℃, 70% relative humidity). Two experimental conditions were set: exercising with surgical face mask (MASK) and without a surgical face mask (CON). The experiment was conducted as a randomized crossover design. Body temperatures, respiratory gas exchange, and subjective indices were measured during exercise. In terms of physiological indices, respiratory rate only revealed a main effect and was significantly lower in the MASK than in CON at 44 min of exercise (CON 41.0±19.2 breaths/min, MASK 35.6±11.2 breaths/min p=0.029). No significant differences were observed between conditions in other physiological parameters. As for the subjective indices, dyspnea showed a condition × time interaction (p=0.016), which was significantly higher in the MASK starting at 5 minutes through the end (CON 4.5±3.5 and MASK 8.5±2.1 at the end of exercise p=0.016). No significant differences were observed in other subjective measures. In conclusion, wearing a surgical face mask during moderate-intensity prolonged exercise under hot environmental conditions significantly worsened dyspnea, but no significant differences were observed in other physiological indices or subjective indices.